Prep, characterisation and structures of nano Flashcards
name 10 different types of synthesis
hydrothermal solvothermal biomimetic electrochemical solvent-free self-assembly templating dip-coating exfoliation and cleavage surface reaction controlled directional
what is hydrothermal synthesis
high temperature aqueous solutions at high vapour pressure to make a crystal
give examples of structures made by hydrothermal synthesis
H2Ti3O7 nanotubes
TiO2 + NaOH at 100C for 3 days - flat sheets rolled into layers using Na+ ions
what is solvothermal synthesis?
pressurised polar solvents at a temp above their bp
how does adding water affect a solvothermal synthesis
makes the single crystals hollow
how do you control size in solvothermal synthesis
via surface protection by organic molecules
give some examples of materials made by solvothermal synthesis
Nanotubes of perovskite
MOF-5
MnO3 crystallites on graphene
What is EEG? and give some properties
electrochemically exfoliated graphene
low level of defects, no O containing surface functional groups, mechanically strong, high conductivity, insoluble in water, soluble in DMF
What is GO? and give some properties
high level of defects, many OH groups, mechanically weak, low conductivity, soluble in water
what is biomimetic synthesis
application of biological principles for materials formation
give some examples of biomimetic synth
hydrothermal growth of ZnO twin-crystals with Gelatin or Gum Arabic
Calcite nanocrystals grown in alienate beads (controls size)
what compounds are made from electrochemical synthesis
anodic aluminium oxide (AAO)
anodic titanium oxide (ATO)
what is the ideal pore base shape according to the equifield strength model?
hemispherical
what is the main structural feature of compounds made by electrochemical synthesis
cylindrical pores
name a mechanism used in solvent-free synthesis
VLS - vapour-liquid-solid
what cal be made by VLS
Si nanowire
what controls the shape of a Si nanowire?
direction controlled by AAO holes, diameter controlled by size of gold
what compound is used for liquid coating to begin a Si nanowire?
SiH4
what is another example of a solvent -free synthesis?
catalytic growth by Co nanoparticles on Mg2SiO2 fibres
or Chemical Vapour Deposition eg carbon encapsulated Co nanoparticles
what is a benefit of chemical vapour deposition
low reaction temperature
low carbon concentration
short rxn time
what is the self-assembly phenomenon
then particles naturally form larger nanostructures
give 3 examples of self-assembly phenomenon
C60 nanowires
self assembly of surfactants used to template formation of mesoporous silicates
monolayer on a metal surface (alkanethiolate on Au(III) substrate)
give 3 examples of templating methods
porous single crystals - make porous structure (KIT-6) and fill with H2Cr2O7
AAO templated Si or Ni nanowire
electron beam induced metal nanowire growth - zeolite containing AgNO3 or CuCl irradiate with e beam giving ag or Cu nanowire.
what are the 5 stages of dip-coating?
1) immersion
2) start-up
3) deposition
4) drainage
5) evaporation of solvent
how do you control thickness of a layer in dip-coating?
depends on how fast substrate pulled out of coating liquid.
what are 3 things that can be made from exfoliation and cleavage methods?
graphene (top-down synthesis) -intercalation of ions followed by exfoliation of layer (by EtOH)
H2Ti3O7 nano sheet unrolled from a nanotube using ligands. nanotube made from crystal layers separated by Na+ ions
disassembly of 3D UTL framework into a 2D lamellae
what is the general shape of a structure formed by a surface reaction controlled by highly selective growth direction?
snowflakes
how to make a snowflake shaped Fe2O3 (hematite)
K3Fe(CH)6 + H2O –> (180C 20h) –> a-Fe2O3
1) nucleation
2)very slow hydrolysis of Fe(CN)6 3-
only grows along 110 directions
give some examples of how to control size and morphology.
nanoparticle by cleavage - thickness of layers and minimum lattice tension
Si wires by AAO - using nanotube template
Dip coating - thickness of liquid film
catalytic growth of Si nanowire - size of catalyst
Porous single crystals - Size of mesopores
C60 nanowires - thickness of solution film
surface protection - reaction rate.
what is braggs law?
n(lambda) = 2dsin(theta)